Reactive astrogliosis is a key component of the cellular response to injury. It has been shown that various molecules are released by reactive astrocytes as a consequence of injury or trauma. Following injury, neurons and astrocytes increase their release of purine nucleosides and nucleotides, which stimulates purinergic receptors that activate signaling pathways and transcription factors. This suggests that nucleotide release might have a regulatory effect on the genes expressed in reactive astrocytes. One such candidate is N-cadherin, a cell adhesion molecule involved in neurite outgrowth. Although it is clear that injury affects N-cadherin expression, little is known about its regulation by purinergic signaling in rat cortical astrocytes. Our preliminary data indicate that N-cadherin is increased following mechanical stretch and by treatment with extracellular ATP and is P2 receptor mediated. Based on these observations, we hypothesize that N-cadherin expression after injury is regulated by purinergic signaling. To test this hypothesis, in vitro and in vivo approaches will be used. In Aim 1, the role of P2 receptors in the regulation of N-cadherin expression will be looked at by treating astrocytes with P2 receptor antagonists prior to injury. As another approach, uninjured cells will be treated with P2 receptor agonists. N-eadherin expression will be determined by immunoblotting. In Aim 2, astrocytes will be pro-treated with inhibitors of MAPK or Akt pathways before injury and N-cadherin levels will be determined with immunoblotting and immunocytochemistry. In Aim 3, a controlled cortical impact model will be used as an in vivo model of trauma to determine if the results obtained in the preliminary section and in Aims 1 and 2 can be extrapolated to an intact system. These studies will provide an insight into the mechanisms that regulate reactive astrogliosis and may contribute to the development of therapeutic strategies to reverse the inhibitory effects of reactive astrogliosis.